\documentclass{article}
\usepackage{polyglossia}
\setdefaultlanguage{english}


%% COMPILE USING XeLaTex


\usepackage{tikz} %To draw
\usetikzlibrary{decorations.pathreplacing}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{positioning}

\begin{document}

\begin{tikzpicture}[xscale=0.42]

% boxes:
\filldraw[fill=black] (15,0) rectangle (25,6pt);
\filldraw[fill=black!20] (0.5,0) rectangle (15,6pt);

% draw horizontal line  
\draw [thick,<->] (0,0) -- (30,0);

% draw vertical lines
  \draw [thick] (15 cm,10pt) -- (15 cm,-6pt);
  \draw [thick] (20 cm,10pt) -- (20 cm,-6pt);
  \draw [thick] (25 cm,10pt) -- (25 cm,-6pt);

% draw nodes
%\node[align=left, above, visible on =<1->]   at (10,10pt) {\small 360,000};
\node[align=center, below] at (15,-0.2) {\small \$360K$-\Delta$};
\node[align=center, below] at (17.5,0.9) {\small \textbf A};

\node[color=black] (main) at (20,2pt) {\small .};
\node[align=center, below] at (20,-0.2) {\small \$360K};

%\node[align=left, above] at (30,10pt) {\small 12,234};
\node[align=center, below] at (25,-0.2) {\small \$360K$+\Delta$};
\node[align=center, below] at (22.5,0.9) {\small \textbf B};

\node[color=black!20, align=left, above] (second) at (5,1pt) {\small .};

\node at (-3,0) {\small Monthly wage};
\node at (-3,-0.3) {\small (CLP\$)};

% connect nodes
%\draw[thick, ->] (main.north) .. controls (12,40pt).. (second.north);

% decoration below main line
\draw [decorate,decoration={brace,amplitude=10pt,mirror,raise=4pt},yshift=0pt] (0,-1) -- (15,-1);
\node[below] at (8,-1.5) {\small Individual type $2$};
%\node[below] at (8,-1.9) {\small No changes in $z_{ig}^1$};

\draw [decorate,decoration={brace,amplitude=10pt,mirror,raise=4pt},yshift=0pt,] (15,-1) -- (25,-1);
\node[below] at (20,-1.5) {\small Individual type $1$};
\node[below] at (20,-1.9) {\small quasi-random assignment};
%

\end{tikzpicture}

\end{document}